Alpha-Adrenergic receptors mediate a number of important functions of the autonomic nervous system including catecholamine-induced arteriolar smooth muscle contraction, hepatic gluconeogenesis and platelet aggregation. Little is known however, about the molecular mechanisms involved in the receptor-catecholamine interaction or in the transduction of information following receptor activation. In addition, the precise role of Alpha1- and Alpha2-receptor in sympathetic neurotransmission and in certain disease states such as hypertension, remains to be defined. Answers to these basic questions will, in part, depend on the elucidation of their structures and physico-chemical properties. We propose, therefore, to isolate and purify Alpha-adrenergic receptors using currently developed novel affinity techniques, chromatofocusing, immunoaffinity chromatography and photoaffinity labeling. The hydrodynamic properties of these highly purified receptor preparations will then be characterized using biophysical techniques as a prerequisite for the ultimate determination of their macromolecular structures. Such characterization should allow a molecular discrimination of the Alpha1- and Alpha2-receptor subtypes to be obtained. Finally, by the use of the purified receptor preparations as immunogens, highly selective and specific antibodies against the receptor binding site will be developed using the Milstein technique of somatic cell fusion. Concurrently, elicited anti-idiotypic anti-receptor antibodies will be raised in rabbits, using conventional procedures. These anti-receptor antibodies will then be used as immunoadsorbents to further aid in the purification of these receptors, and as tools to evaluate hormone-receptor regulation, to define structural differences between the binding sites of Alpha-receptor subtypes and to delineate the contributions of Alpha-receptor mediated sympathetic activity in the genesis of spontaneous hypertension in the rat.